squeezer: Add xalign and yalign
When shrinking a
HdySqueezer, larger widgets will disappear and be replaced by smaller ones. They can disappear with a crossfade animation that will partialy cut them as they are replaced by the smaller widget, and currently they are only cut at the end (equivalent to a 0 x and y alignment).
It would be nice to adjust how they will be aligned, and hence cut, as they are disappearing, e.g. for
HdyViewSwitcherTitle and other centered squeezers we would likely like it to be 0.5, and for a squeezer packed at the start of a horiozontal box maybe we want an xalignment of 1.
I tag it as 1.0 as we may want the 0.5 (centered) behavior to be the default.